U.S. patent application number 12/144702 was filed with the patent office on 2008-10-23 for sheet to form a protective shield for chips.
This patent application is currently assigned to LINTEC CORPORATION. Invention is credited to Hideo Senoo, Takashi Sugino, Osamu Yamazaki.
Application Number | 20080260982 12/144702 |
Document ID | / |
Family ID | 18937369 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080260982 |
Kind Code |
A1 |
Senoo; Hideo ; et
al. |
October 23, 2008 |
Sheet to Form a Protective Shield for Chips
Abstract
A sheet to form a protective film for chips includes a release
sheet and a protective film forming layer formed on a detachable
surface of the release sheet. The protective film forming layer
includes a thermosetting and/or energy ray-curable component and a
binder polymer component.
Inventors: |
Senoo; Hideo;
(Kawaguchi-shi, JP) ; Sugino; Takashi;
(Kawaguchi-shi, JP) ; Yamazaki; Osamu;
(Saitama-shi, JP) |
Correspondence
Address: |
THE WEBB LAW FIRM, P.C.
700 KOPPERS BUILDING, 436 SEVENTH AVENUE
PITTSBURGH
PA
15219
US
|
Assignee: |
LINTEC CORPORATION
Tokyo
JP
|
Family ID: |
18937369 |
Appl. No.: |
12/144702 |
Filed: |
June 24, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11113480 |
Apr 25, 2005 |
7408259 |
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12144702 |
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10102583 |
Mar 20, 2002 |
6919262 |
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11113480 |
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Current U.S.
Class: |
428/40.1 ;
257/E21.599; 257/E23.13; 257/E23.194 |
Current CPC
Class: |
H01L 2221/68327
20130101; H01L 2924/01047 20130101; H01L 2924/01033 20130101; H01L
24/27 20130101; H01L 2224/83855 20130101; H01L 2924/01006 20130101;
H01L 2924/01025 20130101; H01L 23/3164 20130101; H01L 2924/01032
20130101; H01L 21/78 20130101; H01L 2924/01013 20130101; H01L
2924/07802 20130101; H01L 2924/01004 20130101; H01L 2224/2919
20130101; H01L 2924/01005 20130101; H01L 2924/01029 20130101; H01L
2924/0665 20130101; H01L 2224/83191 20130101; H01L 24/29 20130101;
H01L 23/293 20130101; H01L 2924/01079 20130101; H01L 2924/181
20130101; H01L 24/83 20130101; H01L 2924/3025 20130101; H01L
2924/01015 20130101; H01L 2924/01027 20130101; Y10T 428/14
20150115; H01L 21/6836 20130101; H01L 23/562 20130101; H01L
2224/274 20130101; H01L 2924/01019 20130101; H01L 2224/2919
20130101; H01L 2924/0665 20130101; H01L 2224/2919 20130101; H01L
2924/0635 20130101; H01L 2224/2919 20130101; H01L 2924/0665
20130101; H01L 2924/00 20130101; H01L 2924/0665 20130101; H01L
2924/00 20130101; H01L 2924/3512 20130101; H01L 2924/00 20130101;
H01L 2924/181 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
428/40.1 |
International
Class: |
B32B 33/00 20060101
B32B033/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 21, 2001 |
JP |
200181226 |
Claims
1. A sheet to form a protective film for chips comprising a release
sheet and a protective film forming layer formed on a detachable
surface of the release sheet, wherein said protective film forming
layer comprises an energy ray-curable component and a binder
polymer component.
2. The sheet to form a protective film for chips according to claim
1, wherein the binder polymer component is composed of an acrylic
polymer.
3. The sheet to form a protective film for chips according to claim
1, wherein the energy ray-curable component is composed of an
ultraviolet ray-curable resin.
4. A sheet to form a protective film for chips comprising a release
sheet and a protective film forming layer formed on a detachable
surface of the release sheet, wherein said protective film forming
layer comprises a thermosetting component, an energy ray-curable
component and a binder polymer component.
5. The sheet to form a protective film for chips according to claim
4, wherein the binder polymer component is composed of an acrylic
polymer.
6. The sheet to form a protective film for chips according to claim
4, wherein the energy ray-curable component is composed of an
ultraviolet ray-curable resin.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a division of U.S. patent application
Ser. No. 11/113,480 filed Apr. 25, 2005, which is itself a division
of U.S. patent application Ser. No. 10/102,583 filed Mar. 20, 2002,
now U.S. Pat. No. 6,919,262, and also relates to U.S. patent
application Ser. No. 11/113,481 filed Apr. 25, 2005, now U.S. Pat.
No. 7,235,465, all of which are incorporated herein by reference in
their entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a sheet to form a
protective film for chips, which enables to efficiently form a
protective film on a back surface of a semiconductor chip, and
thereby contributes to improvement in production efficiency of
chips. More particularly, the present invention relates to a sheet
to form a protective film for chips, which is used in production of
semiconductor chips by face down mounting process.
[0004] The present invention also relates to a process for
producing semiconductor chips, using the sheet to form a protective
film for chips.
[0005] 2. Description of the Prior Art
[0006] Recently, production of semiconductor devices is made
through a so-called face down mounting process. In the face down
process, chips are electrically connected with a substrate through
a convex portion (bump) formed on a circuit surface of the chip to
ensure its conductivity to the substrate.
[0007] Semiconductor devices are generally produced through the
following steps:
[0008] (1) forming a circuit on a surface of a semiconductor wafer
by etching or the like and providing a bump on the appointed
position of the circuit surface;
[0009] (2) grinding a back surface of the semiconductor wafer to
have a given thickness;
[0010] (3) fixing the back surface of the semiconductor wafer onto
a dicing sheet which is tautly supported by a ring frame, and
dicing the wafer to separate each circuit by the use of a dicing
saw to obtain semiconductor chips; and
[0011] (4) picking up the semiconductor chips to mount them face
down on a prescribed substrate and sealing the chip in a resin or
coating the back surface of the chip with a resin according to
necessity for chip protection, thereby obtaining a semiconductor
device.
[0012] The resin sealing is performed by dripping resin in a proper
amount on the chip (potting method) or using a mold (molding
method), both followed by curing. The potting method has a drawback
of difficulty in dripping a proper amount of resin. The molding
method involves washing of the mold, which will require additional
costs for equipment and operation thereof.
[0013] The resin coating may cause ununiform quality because of the
difficulty in spreading a proper amount of resin evenly on the
chips.
[0014] Therefore, the technique which is capable of forming a
highly uniform protective film on a back surface of the chip by
simplified operation has been desired.
[0015] In the grinding of the back surface of the wafer in step
(2), minute streaky scratches are formed on the back surface of the
chip owing to the use of a grinding machine. The minute scratches
may cause cracks during the dicing in step (3) or after the device
is packaged. As such, it has been conventionally required in some
cases to perform chemical etching after the mechanical grinding to
eliminate the minute scratches. The chemical etching, as a matter
of course, raises problems related to the cost increase for its
equipment and operation.
[0016] Therefore, the technique for prevailing adverse effects
resulting from minute scratches has been desired, even if minute
scratches are left on the back surface of the wafer as a result of
mechanical grinding.
[0017] In light of the above prior art, it is an object of the
present invention to provide a process through which a highly
uniform protective film can be readily formed on a back surface of
the chip, and, even if minute scratches are formed on the back
surface of the chip as a result of mechanical grinding, the chip is
prevailed over adverse effects resulting from the scratches. It is
another object of the invention to provide a sheet to form a
protective film for chips employable in the above process.
SUMMARY OF THE INVENTION
[0018] A first sheet to form a protective film for chips according
to the present invention comprises a release sheet and a protective
film forming layer formed on a detachable surface of the release
sheet, wherein said protective film forming layer comprises a
thermosetting or energy ray-curable component and a binder polymer
component.
[0019] A second sheet to form a protective film for chips according
to the present invention comprises a release sheet and a protective
film forming layer formed on a detachable surface of the release
sheet, wherein said protective film forming layer comprises a
thermosetting component, an energy ray-curable component and a
binder polymer component.
[0020] In the invention, the binder polymer component, the
thermosetting component and the energy ray-curable component are
preferably composed of an acrylic polymer, an epoxy resin and an
ultraviolet ray-curable resin, respectively.
[0021] When the sheet to form a protective film for chips is
employed in the process of the invention (mentioned later), a
highly uniform protective film can be readily formed on a back
surface of the chip and, even if minute scratches are formed on the
back surface of the chip as a result of mechanical grinding, the
chip is prevailed over adverse effects resulting from the
scratches.
[0022] The first process for producing semiconductor chips having a
protective film on the back surface comprises:
[0023] adhering a protective film forming layer of the first or
second sheet to form a protective film for chips according to the
present invention onto a back surface of a semiconductor wafer
having circuits on its surface, and thereafter, further conducting
the following steps 1 to 3 in an arbitrary order:
[0024] Step 1: detaching the release sheet from the protective film
forming layer;
[0025] Step 2: curing the protective film forming layer by heating
or energy ray irradiation;
[0026] Step 3: dicing the semiconductor wafer together with the
protective film forming layer with respect to each circuit.
[0027] The second process for producing semiconductor chips having
a protective film on the back surface comprises:
[0028] adhering a protective film forming layer of the second sheet
to form a protective film for chips according to the present
invention onto a back surface of a semiconductor wafer having
circuits on its surface,
[0029] curing the protective film forming layer by irradiation with
energy ray, and thereafter, further conducting the following steps
1 to 3 in an arbitrary order:
[0030] Step 1: detaching the release sheet from the protective film
forming layer;
[0031] Step 2: further curing the protective film forming layer by
heating;
[0032] Step 3: dicing the semiconductor wafer together with the
protective film forming layer with respect to each circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a section view of the sheet to form a protective
film for chips of the present invention;
[0034] FIGS. 2 to 7 are flow sheets of processes for producing
semiconductor chips of the present invention;
DETAILED DESCRIPTION OF THE INVENTION
[0035] The present invention will be described in detail with
reference to the drawings.
[0036] The first sheet 10 to form a protective film for chips of
the invention comprises, as shown in FIG. 1, the release sheet 1
and the protective film forming layer 2 formed on a detachable
surface of the release sheet 1.
[0037] The release sheet 1 can be composed of a film of, e.g.,
polyethylene, polypropylene, polybutene, polybutadiene,
polymethylpentene, polyvinyl chloride, vinyl chloride copolymer,
polyethylene terephthalate, polyethylene naphthalate, polybutylene
terephthalate, polyurethane, ethylene-vinyl acetate, ionomer-resin,
ethylene/(meth)acrylic acid copolymer, ethylene/(meth)acrylate
copolymer, polystyrene, polycarbonate, polyimide, and fluorine
resin. A film of a crosslinked product of the above polymers, or a
laminated film of the above films can be used as well.
[0038] When the release sheet is detached after the curing of the
protective film forming layer, films of polymethylpentene,
polyethylene naphthalate and polyimide are particularly preferable
for their excellent heat resistance.
[0039] The release sheet 1 has a surface tension of 40 mN/m or
less, preferably 37 mN/m or less, highly preferably 35 mN/m or
less. The low surface tension of the release sheet 1 can be
attained by appropriately selecting the sheet material or coating a
silicone resin on the surface of sheet 1 for release treatment.
[0040] The release sheet 1 has a thickness of generally 5 to 300
.mu.m, preferably 10 to 200 .mu.m, particularly preferably 20 to
150 .mu.m.
[0041] The protective film forming layer 2 of the first sheet to
form a protective film for chips is composed of a thermosetting or
energy ray-curable component and a binder polymer component.
[0042] The protective film forming layer 2 of the second sheet to
form a protective film for chips is composed of a thermosetting
component, an energy ray-curable component and a binder polymer
component.
[0043] Examples of the thermosetting component include epoxy resin,
phenol resin, melamine resin, urea resin, polyester resin, urethane
resin, acrylic resin, polyimide resin, benzoxazine resin and
mixtures thereof. In the invention, epoxy resin, phenol resin and a
mixture thereof are preferably employed.
[0044] The epoxy resin can make a rigid coat with three dimensional
network when heated. Various known epoxy resins have been
conventionally used. Preferably, the epoxy resin has a molecular
weight of around 300 to 2000. Particularly preferred is a blend of
epoxy resins containing a liquid one in an ordinary state, having a
molecular weight of 300 to 500, preferably 330 to 400 and the solid
one at ordinary temperature, having a molecular weight of 400 to
2500, preferably 500 to 2000. The epoxy resin preferably used in
the invention has an epoxy equivalent of 50 to 5000 g/eq. Examples
for such epoxy resin include glycidyl ethers of phenol, e.g.,
bisphenol A, bisphenol F, resorcinol, phenol novolak and cresol
novolak; glycidyl ethers of alcohol, e.g., butanediol, polyethylene
glycol and polypropylene glycol; glycidyl ethers of carboxylic
acid, e.g., phthalic acid, isophthalic acid and tetrahydrophthalic
acid; epoxy resins of the glycidyl- or alkyl glycidyl-type, e.g.,
those of aniline isocyanurate in which active hydrogen bonded to
nitrogen is substituted with a glycidyl group; and so-called
alicyclic epoxides in which epoxy is introduced by oxidation of
C--C double bond in the molecule, e.g., vinylcyclohexane diepoxide,
3,4-epoxycyclohexylmethyl-e,4-dicyclohexane carboxylate and
2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohenane-m-dioxane.
Epoxy resins having a biphenyl, dicyclohexadiene or naphthalene
skeleton can be also employed.
[0045] Of these, epoxy resins of bisphenol-based glycidyl type,
o-cresol novolak type or phenol novolak type are preferable for the
invention. These epoxy resins are used either individually or in
combination.
[0046] The epoxy resin, when employed, is used together with an
assistant additive, i.e., a heat-activatable latent epoxy resin
curing agent, preferably.
[0047] The heat-activatable latent epoxy resin curing agent does
not react with an epoxy resin at room temperature but does react
when activated under heating over a specific temperature.
[0048] To activate the heat-activatable latent epoxy resin curing
agent, use can be made of a method in which active species (anions,
cations) are generated through the chemical reaction by heating, a
method in which the agent, which has been stably dispersed in the
epoxy resin at around room temperature, is incorporated with the
resin to dissolve therein at high temperatures to initiate the
curing reaction, a method in which the curing agent encapsulated in
a molecular sieve is eluted at high temperatures to initiate the
curing reaction, and a method using a micro-capsule.
[0049] Examples of the heat-activatable latent epoxy resin curing
agent for use in the invention include various onium salts and
active hydrogen compounds of high melting point, e.g., dibasic acid
dihydrazide compound, dicyandiamide, amine adduct curing agent and
imidazole compound.
[0050] These heat-activatable latent epoxy resin curing agents can
be used either individually or in combination. The heat-activatable
latent epoxy resin curing agent is used at 0.1 to 20 parts,
preferably 0.2 to 10 parts, highly preferably 0.3 to 5 parts by
weight per 100 parts by weight of the epoxy resin.
[0051] Condensation products of aldehydes and phenols, e.g.,
alkylphenol, polyphenol and naphthol, can be used as the phenol
resin without limitations. Examples of the phenol resin preferably
us3ed in the invention include phenol novolak, o-cresol novolak,
p-cresol novolak, t-butyl phenol novolak, dicyclopentadiene cresol,
poly paravinyl phenol and bisphenol A novolak resins, and modified
resins thereof.
[0052] The phenolic hydroxyl group contained in the phenol resin
can readily occur addition reaction with an epoxy group in the
epoxy resin when heated to form a cured product high in impact
resistance. Accordingly, the epoxy resin and the phenol resin can
be used together.
[0053] The energy ray-curable component is composed of a compound
polymerizable/curable by irradiation of an energy ray, e.g.,
ultraviolet ray and electron ray. The compound has at least one
polymerizable double bond in the molecule, and generally has a
molecular weight of around 100 to 30000, preferably around 300 to
10000. Exemplary compounds polymerizable by energy ray irradiation
include low molecular weight compounds disclosed in Japanese Patent
Laid-Open Publication Nos. 60(1985)/196956 and 60(1985)/223139.
Specifically, examples include trimethylolpropane triacrylate,
tetramethylolmethane tetraacrylate, pentaerythritol triacrylate,
dipentaerythritol monohydroxypentaacrylate, dipentaerythritol
hexaacrylate, 1,4-butyleneglycoldiacrylate,
1,6-hexanedioldiacrylate, polyethyleneglycoldiacrylate,
oligoesteracrylate, a urethaneacrylate oligomer of polyester or
polyether type, polyesteracrylate, polyetheracrylate, and
epoxy-modified acrylate.
[0054] Of these, preferable for the present invention are
ultraviolet ray-curable resins, specifically oligoesteracrylate and
a urethaneacrylate oligomer.
[0055] Incorporation of a photopolymerization initiator in the
energy ray-curable component can shorten the polymerization/curing
time and reduce the ray irradiation dose.
[0056] Examples of the photopolymerization initiator include
benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin
ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether,
benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl
ketal, 2,4-diethylthioxanthone,
.alpha.-hydroxycyclohexylphenylketone, benzyldiphenylsulfide,
tetramethylthiurammonosulfide, azobisisobutyronitrile, benzyl,
dibenzyl, diacetyl, and .beta.-chloroanthraquinone.
[0057] The photopolymerization initiator is suitably used at 1.5 to
4.5 parts by weight, preferably 2.4 to 3.8 parts by weight per 100
parts by weight of the energy ray-curable component.
[0058] The binder polymer component is employed for the purposes of
imparting proper tackiness to the protective film forming layer 2
and improving operability of the sheet.
[0059] The binder polymer has a weight-average molecular weight of
50,000 to 2,000,000, preferably 100,000 to 1,500,000, particularly
preferably 200,000 to 1,000,000. The sheet might not be formed
adequately when the molecular weight of the binder polymer is too
low, and not uniformly when too high because of poor mutual
solubility of the polymer with other components.
[0060] Usable binder polymers are, for example, acrylic polymers,
polyester resin, urethane resin, silicone resin and rubber
polymers. Acrylic polymers are preferable.
[0061] Examples of the acrylic polymers include (meth)acrylate
copolymers comprising constituent units derived from a
(meth)acrylate monomer and those derived from a (meth)acrylic acid
derivative. Preferably, the (meth)acrylate monomer is C.sub.1-18
alkyl (meth)acrylate, e.g., methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate and butyl (meth)acrylate.
Exemplary (meth)acrylic acid derivatives are (meth)acrylic acid,
glycidyl (meth)acrylate and hydroxyethyl (meth)acrylate.
[0062] A glycidyl group may be introduced into the acrylic polymer
chain by copolymerization of glycidyl (meth)acrylate, thereby
improving mutual solubility of the polymer with an epoxy resin
working as a thermosetting adhesive component (mentioned later).
The copolymerization also increases Tg of the cured product,
thereby improving the heat resistance. Introducing a hydroxyl group
into the acrylic polymer using, for example, hydroxyethyl acrylate
facilitates controlling the adhesion toward a chip and adhesion
characteristics of the polymer.
[0063] The acrylic polymer has a weight average molecular weight of
preferably 100,000 or more, more preferably 150,000 to 1,000,000.
The glass transition temperature thereof is usually 20.degree. C.
or below, preferably around -70 to 0.degree. C. The polymer has
tackiness at ordinary temperature (23.degree. C.).
[0064] Referring to the first sheet to form a protective film for
chips, when the thermosetting component alone is incorporated in
the protective film forming layer 2, it is incorporated at usually
100 to 1500 parts, preferably 150 to 1000 parts, more preferably
200 to 800 parts by weight per 100 parts by weight of the binder
polymer component. When the energy ray-curable component alone is
incorporated in the protective film forming layer 2, it is
incorporated at 5 to 500 parts, preferably 10 to 200 parts, more
preferably 20 to 150 parts by weight per 100 parts by weight of the
binder polymer component.
[0065] Referring to the second sheet to form a protective film for
chips, the thermosetting component and the energy ray-curable
component are incorporated in the protective film forming layer 2
at 100 to 1500 parts, preferably 150 to 1000 parts, more preferably
200 to 800 parts by weight in total per 100 parts by weight of the
binder polymer component. At the same time, the weight ratio of the
thermosetting component to the energy ray-curable component
(thermosetting component/energy ray-curable component) is
preferably 55/45 to 97/3, more preferably 60/40 to 95/5,
particularly preferably 70/30 to 90/10.
[0066] Incorporation of the thermosetting component and the energy
ray-curable component with the binder polymer component in the
above weight ratio gives a protective film which has proper
tackiness before curing to allow secure application and exhibits
excellent film hardness after curing.
[0067] The protective film forming layer 2 can be colored.
Coloration for the protective film forming layer 2 can be made by
incorporating a pigment or a dye therein. The colored protective
film forming layer 2 improves appearance of the resulting
chips.
[0068] The protective film forming layer 2 may contain various
additives in addition to the above components. For example,
electrically conductive fillers, e.g., gold, silver, copper,
nickel, aluminum, stainless steel, carbon, ceramic, silver-coated
nickel and silver-coated aluminum are added for the purpose of
imparting electrical conductivity after die bonding. Thermal
conductive substances, such as metallic materials, e.g., gold,
silver, copper, nickel, aluminum, stainless steel, silicon and
germanium, and alloys thereof, are added for the purpose of
imparting thermal conductivity.
[0069] A coupling agent may be added in the protective film forming
layer 2 to improve adhesive properties and adhesion between the
back surface of the chip and the cured protective film. The
coupling agent improves adhesive properties, adhesion and water
resistance (moist heat resistance) of the protective film without
deteriorating its heat resistance.
[0070] A preferable coupling agent is of silane type (silane
coupling agent) in view of versatility and costwise merits.
[0071] The protective film forming layer 2 may contain a
crosslinking agent, e.g., organic polyvalent isocyanate compound,
organic polyvalent imine compound and organometallic chelate
compound, to adjust its initial adhesive and cohesive forces before
cure.
[0072] An antistatic agent may be incorporated in the protective
film forming layer 2. Incorporation thereof inhibits static
electricity occurrence to improve the chip reliability.
[0073] A phosphoric acid, bromo or phosphorus compound can be
incorporated in the protective film forming layer 2 to impart flame
resistance. Such a film has improved reliability as a manufactured
IC package.
[0074] The sheet 10 to form a protective film for chips is produced
by coating the composition comprising the above components directly
on a detachable surface of the release sheet 1 using a conventional
coater, e.g., a roll knife coater, a gravure coater, a die coater
and a reverse coater, or by transferring said composition on a
detachable surface of the release sheet 1, and drying the
composition to form the protective film forming layer 2. The
composition can be coated on the detachable surface of the release
sheet in a state dissolved or dispersed in a solvent according to
necessity.
[0075] The protective film forming layer 2 thus formed has a
thickness of usually 3 to 100 .mu.m, preferably 10 to 60 .mu.m.
[0076] The second sheet to form a protective film for chips of the
present invention has common features, preferable embodiments
inclusive, with the first sheet to form a protective film for
chips, except that the former sheet has the protective film forming
layer composed essentially of both thermosetting and energy
ray-curable components.
[0077] The first or second sheet 10 to form a protective film for
chips, when employed in the process for producing semiconductor
devices (mentioned later), can readily make a highly uniform
protective film on a back surface of a chip. Moreover, even if
minute scratches are formed on the back surface of the chip as a
result of mechanical grinding, the chip is prevailed over adverse
effects resulting from the scratches.
[0078] The first process for producing semiconductor chips of the
present invention will beg described with reference to the
drawings.
[0079] The first process for producing semiconductor chips having a
protective film on the back surface comprises:
[0080] adhering a protective film forming layer of the first or
second sheet to form a protective film for chips according to the
present invention onto a back surface of a semiconductor wafer
having circuits on its surface, and thereafter, further conducting
the following steps 1 to 3 in an arbitrary order:
[0081] Step 1: detaching the release sheet from the protective film
forming layer;
[0082] Step 2: curing the protective film forming layer by heating
or energy ray irradiation;
[0083] Step 3: dicing the semiconductor wafer together with the
protective film forming layer with respect to each circuit.
[0084] The process wherein the steps 1, 2 and 3 are conducted in
this order (hereinafter, referred to as 1-2-3 mode production
process) is first described with reference to FIG. 2.
[0085] The protective film forming layer 2 of the sheet 10 to form
a protective film for chips is applied onto a back surface of the
semiconductor wafer 3 having circuits on its surface (FIG.
2-A).
[0086] The release sheet 1 IS DETACHED FROM THE PROTECTIVE FILM
FORMING LAYER 2, AS SHOWN IN FIG. 2-B, to obtain a laminate
composed of the semiconductor wafer 3 and the protective film
forming layer 2.
[0087] Then, the protective film forming layer 2 is cured by
heating or energy ray irradiation to form a protective film
covering all the back surface of the wafer. FIG. 2-C illustrates
the feature wherein the protective film forming layer 2 is heated
using a heating apparatus. The wafer with the protective film has
higher strength compared with the naked one, thereby decreasing
breakage of the wafer during operation. Even if minute scratches
are formed on the back surface of the wafer as a result of
grinding, the protective film fills in the scratches, thereby
prevailing the wafer over adverse effects resulting from the
scratches.
[0088] The protective film of the invention is excellent in
thickness uniformity and the yield of its materials in comparison
with protective films produced by spreading a coating liquid
directly on a back surface of the wafer or chip to make a
protective film.
[0089] Next, as shown in FIG. 2-D, the laminate composed of the
semiconductor wafer 3 and the protective film 2 is diced with
respect to each circuit formed on the wafer surface. The dicing is
performed so as to cut both of the wafer and the protective film.
The wafer dicing is performed by the conventional method using a
dicing sheet. As a result, semiconductor chips having a protective
film on its back surface are obtained.
[0090] Finally, diced chips are picked up by the use of general
means, e.g., collets, thereby semiconductor chips having a
protective film on its back surface are obtained (FIG. 2-E).
[0091] According to the invention, a highly uniform protective film
can be readily formed on a back surface of a chip, and even if
minute scratches are formed on the back surface of the chip as a
result of mechanical grinding, the protective film fills in the
scratches, thereby reducing the occurrence of cracks during the
dicing step or in the finally packaged device.
[0092] The process wherein the steps 1, 3 and 2 are conducted in
this order is described in detail below with reference to FIG.
3.
[0093] The 1-3-2 mode production process comprises the steps
of:
[0094] applying the protective film forming layer 2 of the sheet 10
to form a protective film for chips onto the back surface of the
semiconductor wafer 3 having circuits on its surface (FIG.
3-A);
[0095] detaching the release sheet 1 from the protective film
forming layer 2 (FIG. 3-B);
[0096] dicing the semiconductor wafer 3 together with the
protective film 2 with respect to each circuit (FIG. 3C); and
[0097] curing the protective film forming layer 2 by heating or
energy ray irradiation (FIG. 3-D) to obtain semiconductor chips
having the protective film 2 on its back surface (FIG. 3-E).
[0098] That is, the 1-3-2 mode production process is identical to
the 1-2-3 mode production process (FIG. 2), except that the
protective film forming layer 2 is cured after the dicing.
[0099] When the protective film forming layer 2 contains the
thermosetting component, the curing thereof is conducted by
heating. Therefore, the dicing sheet is required to have sufficient
heat resistance to avoid heat deterioration at the time of
curing.
[0100] The process wherein the steps 2, 1 and 3 are conducted in
this order is described in detail with reference to FIG. 4.
[0101] The 2-1-3 mode production process comprises the steps
of:
[0102] applying the protective film forming layer 2 of the sheet 10
to form a protective film for chips onto the back surface of the
semiconductor wafer 3 having circuits on its surface (FIG.
4-A);
[0103] curing the protective film forming layer 2 by heating or
energy ray irradiation (FIG. 4-B);
[0104] detaching the release sheet 1 from the cured protective film
forming layer 2 (FIG. 4-C); and
[0105] dicing the semiconductor wafer 3 together with the
protective film 2 with respect to each circuit (FIG. 4-D) to obtain
semiconductor chips having the protective film 2 on its back
surface (FIG. 4-E).
[0106] That is, the 2-1-3 mode production process is identical to
the 1-2-3 mode production process, except that the release sheet 1
is detached after the protective film forming layer 2 is cured.
[0107] When the protective film forming layer 2 contains the
thermosetting component, the curing thereof is conducted by
heating. Therefore, the release sheet 1 is required to have
sufficient heat resistance to avoid heat deterioration at the time
of curing. Hence, films of, e.g., polymethylpentene, polyethylene
naphthalate and polyimide, are employed as the release sheet 1
because of their excellent heat resistance.
[0108] The process wherein the steps 2, 3 and 1 are conducted in
this order is described in detail with reference to FIG. 5.
[0109] The 2-3-1 mode production process comprises the steps
of:
[0110] applying the protective film forming layer 2 of the sheet 10
to form a protective film for chips onto the back surface of the
semiconductor wafer 3 having circuits on its surface (FIG.
5-A);
[0111] curing the protective film forming layer 2 by heating or
energy ray irradiation (FIG. 5B);
[0112] dicing the semiconductor wafer 3 together with the cured
protective film forming layer 2 with respect to each circuit (FIG.
5-C); and
[0113] detaching the release sheet 1 from the cured protective film
forming layer 2 (FIG. 5-D) to obtain semiconductor chips having the
protective film 2 on its back surface.
[0114] In this mode, the detaching of the release sheet 1
synchronizes with the picking up of the chip. In other words, by
picking up the chip, the chip is detached from the release sheet to
give a semiconductor chip having the protective film on its back
surface.
[0115] When the protective film forming layer 2 contains the
thermosetting component, the curing thereof is conducted by
heating. Therefore, the release sheet 1 is required to have
sufficient heat resistance to avoid heat deterioration at the time
of curing. Hence, films of, e.g., polymethylpentene, polyethylene
naphthalate and polyimide, are employed as the release sheet 1
because of their excellent heat resistance.
[0116] The process wherein the steps 3, 1 and 2 are conducted in
this order is described in detail with reference to FIG. 6.
[0117] The 3-1-2 mode production process comprises the steps
of:
[0118] applying the protective film forming layer 2 of the sheet 10
to form a protective film for chips onto the back surface of the
semiconductor wafer 3 having circuits on its surface;
[0119] dicing the semiconductor wafer 3 together with the
protective film forming layer 2 with respect to each circuit;
[0120] detaching the release sheet 1 from the protective film
forming layer 2; and
[0121] curing the protective film forming layer 2 by heating or
energy ray irradiation to obtain semiconductor chips having the
protective film on its back surface.
[0122] As shown in FIGS. 6-A to 6-C, this mode enables the dicing
of the wafer 3 fixed on the protective film forming layer 2. In
this case, the sheet 10 to form a protective film for chips has a
function to act as a so-called dicing sheet. However, when the chip
is mounted on a substrate for chips, the protective film forming
layer has been already cured, losing the ability to act as a die
bonding. Accordingly, the sheet employed in the process for
producing semiconductor chips of the invention cannot be used as a
dicing/die-bonding sheet.
[0123] The sheet 10 to form a protective film for chips fixing the
wafer 3 on its protective film forming layer 2 can be fixed on a
dicing sheet, as shown in FIGS. 6-D to 6-F, to go through the above
procedures.
[0124] According to the present invention, a highly uniform
protective film can be readily formed on a back surface of a
chip.
[0125] The process wherein the steps 3, 2 and 1 are conducted in
this order is described in detail with reference to FIG. 7.
[0126] The 3-2-1 mode production process comprises the steps
of:
[0127] applying the protective film forming layer 2 of the sheet 10
to form a protective film for chips onto the back surface of the
semiconductor wafer 3 having circuits on its surface;
[0128] dicing the semiconductor wafer 3 together with the
protective film forming layer 2 with respect to each circuit;
[0129] curing the protective film forming layer 2 by heating or
energy ray irradiation; and
[0130] detaching the release sheet 1 from the cured protective film
forming layer 2 to obtain semiconductor chips having the protective
film on its back surface.
[0131] That is, the 3-2-1 mode production process is identical to
the 3-1-2 mode production process (FIG. 6), except that the release
sheet 1 is detached from the protective film forming layer 2 after
the protective film forming layer 2 is cured.
[0132] As is mentioned earlier, the steps 1 to 3 can be performed
in an arbitrary order without limitations in the first production
process. Preferably, they are performed in the order of 1-2-3,
2-1-3, 3-1-2 or 3-2-1.
[0133] FIGS. 2 to 7 illustrate the case where the curing for the
protective film forming layer is conducted by the use of a heating
apparatus. When the energy ray-curable component is used as the
curable component, the curing is performed using an energy ray
irradiation equipment (ultraviolet ray irradiation equipment when
ultraviolet ray being the energy ray).
[0134] In the case where the second sheet to form a protective film
for chips is used, the protective film forming layer comprising
both the thermosetting component and the energy ray-curable
component as the curable component is cured by heating and energy
ray irradiation, which can be performed simultaneously or
successively. Preferably, the protective film forming layer formed
on a back surface of the wafer is first half cured by energy ray
irradiation and then completely by heating to make a protective
film.
[0135] The second process for producing semiconductor chips having
a protective film on the back surface comprises:
[0136] adhering a protective film forming layer of the second sheet
to form a protective film for chips according to the present
invention onto a back surface of a semiconductor wafer having
circuits on its surface,
[0137] curing the protective film forming layer by irradiation with
energy ray, and thereafter, further conducting the following steps
1 to 3 in an arbitrary order:
[0138] Step 1: detaching the release sheet from the protective film
forming layer;
[0139] Step 2: further curing the protective film forming layer by
heating;
[0140] Step 3: dicing the semiconductor wafer together with the
protective film forming layer with respect to each circuit.
[0141] The steps 1 to 3 can be performed in an arbitrary order
without limitations in the second production process likewise in
the first production process. Preferably, they are performed in the
order of 1-2-3, 2-1-3, 3-1-2 or 3-2-1.
[0142] When the protective film forming layer is cured by energy
ray irradiation, the protective film forming layer loses tackiness
and never sticks to other members even by the contact with other
members under the usual storage conditions. Therefore, the series
of the steps can be securely carried out to thereby improve the
workability.
[0143] According to the present invention, a highly uniform
protective film can be readily formed on a back surface of a chip,
and, even if minute scratches are formed on the back surface of the
chip as a result of mechanical grinding, the chip is prevailed over
adverse effects resulting from the scratches.
EXAMPLES
[0144] The present invention is described in detail with reference
to the examples, which are not to limit the scopes of the invention
in any way. The composition of the protective film forming layer,
the wafer and the apparatuses used in the examples are shown
below.
Protective Film Forming Layer 1
[0145] The protective film forming layer 1 was composed of a
composition comprising:
[0146] 15 parts by weight of a binder polymer composed of an
acrylic polymer (a copolymer composed of 55 parts by weight of
butyl acrylate, 15 parts by weight of methyl methacrylate, 20 parts
by weight of glycidyl methacrylate and 5 parts by weight of
2-hydroxyethyl acrylate, and having a weight average molecular
weight of 900,000 and a glass transition temperature of -28.degree.
C.,
[0147] 80 parts by weight of a thermosetting component composed of
a mixed epoxy resin (30 parts by weight of a liquid epoxy-bisphenol
A resin (epoxy equivalent: 180 TO 200), 40 parts by weight of a
solid epoxy-bisphenol a resin (epoxy equivalent: 800 to 900) and 10
parts by weight of an epoxy-o-cresol novolak resin (epoxy
equivalent: 210 to 230),
[0148] 0.6 part by weight of a heat-activatable latent epoxy resin
curing agent (amine adduct type),
[0149] 1.3 parts by weight of a black pigment (azo type), and a
diluent solvent.
Protective Film Forming Layer 2
[0150] The protective film forming layer 2 was composed of a
composition comprising, in addition to the composition for the
protective film forming layer 1:
[0151] 15 parts by weight of an energy ray (ultraviolet ray)
curable component (trimethylolpropane triacrylate) and
[0152] 4.5 parts by weight of a photopolymerization initiator
(.alpha.-hydroxycyclohexylphenylketone).
Protective Film Forming Layer 3
[0153] The protective film forming layer 3 was composed of a
composition comprising:
[0154] 100 parts by weight of a binder polymer composed of an
acrylic polymer (a copolymer composed of 65 parts by weight of
butyl acrylate, 10 parts by weight of methyl methacrylate, 10 parts
by weight of methyl acrylate and 15 parts by weight of
2-hydroxyethyl acrylate, and having a weight average molecular
weight of 800,000 and a glass transition temperature of -33.degree.
C.),
[0155] 50 parts by weight of an energy ray (ultraviolet ray)
curable component (trimethylolpropane triacrylate),
[0156] 1.5 parts by weight of a photocurable component
(.alpha.-hydroxycyclohexylphenylketone).
[0157] 0.5 part by weight of a crosslinking agent (organic
polyvalent isocyanato-based crosslinking agent (Coronate L, Nippon
Polyurethane Industry Co., Ltd.)), and
[0158] a diluent solvent.
Wafer
[0159] An underground wafer having a diameter of six inches was
ground to a thickness of 200 .mu.m using a grinding apparatus
(Disco Co., DFG-840) at #2000 abrasion to prepare the wafer for the
examples.
Sheet Applying Apparatus
[0160] Adwill RAD3500m/12 (Lintec Co., Ltd.)
Sheet Detaching Apparatus
[0161] Adwill RAD3000m/12 (Lintec Co., Ltd.)
Dicing Tape Mounter
[0162] Adwill RAD2500m/8 (Lintec Co., Ltd.)
Ultraviolet Ray Irradiation Apparatus
[0163] Adwill RAD2000m/8 (Lintec Co., Ltd.)
Dicing Apparatus
[0164] AWD4000B (Tokyo Seimitsu Co., Ltd.)
Forced Convection Constant Temperature Oven
[0165] DN610 (Yamato Scientific Co., Ltd.)
Dicing Sheet
[0166] Adwill G-11 (Lintec Co., Ltd.)
Example 1
[0167] A polyethyleneterephthalate film (Lintec Co., Ltd.
SP-PET3811), thickness: 38 .mu.m, surface tension: less than 30
mN/m) having been treated for releasing at one surface was used as
a release sheet. The composition for the protective film forming
layer 1 was coated on the release-treated surface of the release
sheet so as to have a thickness of 30 .mu.m after the solvent being
removed by drying, thereby a sheet to form a protective film for
chips was prepared. For protection of the coated surface, a
release-treated polyethyleneterephthalate film (Lintec Co., Ltd.
SP-PET3801) was laminated thereon.
[0168] The polyethyleneterephthalate film (SP-PET3801) was detached
from the sheet to form a protective film for chips. The protective
film forming layer was applied onto the ground surface of the wafer
using the sheet applying apparatus. The peripheral edge of the
sheet was removed along the wafer shape (FIG. 2A). The release
sheet was detached using the sheet detaching apparatus (FIG. 2-B).
The protective film forming layer was cured by heating at
160.degree. C. for 1 hour using the forced convection constant
temperature oven (FIG. 2-C) to prepare a wafer having a protective
film.
[0169] A dicing sheet was applied on the protective film of the
wafer using the dicing tape mounter. The wafer, together with the
protective film, was diced into chips (10 mm.times.10 mm) by the
use of the dicing apparatus to obtain objective chips having a
protective film (FIGS. 2-D and 2-E).
Example 2
[0170] A polyethylenenaphthalate film (Teijin Ltd., Teonex),
thickness: 25 .mu.m, surface tension: less than 30 mN/m having been
treated for releasing at one surface was used as a release sheet.
The composition for the protective film forming layer 1 was coated
on the release-treated surface of the release sheet so as to have a
thickness of 30 .mu.m after the solvent being removed by drying,
thereby a sheet to form a protective film for chips was prepared.
For protection of the coated surface, a release-treated
polyethyleneterephthalate film (Lintec Co., Ltd. SP-PET3801) was
laminated thereon.
[0171] The polyethyleneterephthalate film was detached from the
sheet to form a protective film for chips. The sheet was applied on
the ground surface of the wafer in the same manner as in Example 1.
The peripheral edge of the sheet was removed along the wafer shape
(FIG. 4-A).
[0172] The protective film forming layer was cured by heating at
160.degree. C. for 1 hour using the forced convection constant
temperature oven (FIG. 4-B) to form a protective film on the ground
surface of the wafer.
[0173] The release sheet was detached using the sheet detaching
apparatus (FIG. 4-C). A dicing sheet was applied on the protective
film of the wafer using the dicing tape mounter. The wafer,
together with the protective film, was diced into chips (10
mm.times.10 mm) by the use of the dicing apparatus to obtain
objective chips having a protective film (FIGS. 4-D and 4-E).
Example 3
[0174] A polyethyleneterephthalate film (Lintec Co., Ltd.
SP-PET3811 having been treated for releasing at one side was used
as a release sheet. The composition for the protective film forming
layer 3 was coated on the release-treated surface of the release
sheet so as to have a thickness of 30 .mu.m after the solvent has
been removed by drying, thereby a sheet to form a protective film
for chips was prepared. For protection of the coated surface, a
release-treated polyethyleneterephthalate film (Lintec Co., Ltd.
SP-PET3801) was laminated thereon.
[0175] The polyethyleneterephthalate film (SP-PET3801) was detached
from the sheet to form a protective film for chips. The sheet was
applied on the ground surface of the wafer in the same manner as in
Example 1. The peripheral edge of the sheet was removed along the
wafer shape (FIG. 4-A).
[0176] The protective film forming layer was completely cured by
ultraviolet ray irradiation dosed form the sheet side using the
ultraviolet ray irradiation apparatus, thereby a wafer having a
protective film was obtained (not shown in the figure).
[0177] The release sheet was detached using the sheet detaching
apparatus (FIG. 4-C). A dicing sheet was applied onto the
protective film of the wafer using the dicing tape mounter. The
wafer, together with the protective film, was diced into chips (10
mm.times.10 mm) using the dicing apparatus to obtain objective
chips having a protective film (FIGS. 4-D and 4-E).
Example 4
[0178] The composition for the protective film forming layer 2 was
coated on the release-treated surface of a
polyethyleneterephthalate film (Lintec Co., Ltd. SP-PET3801) having
been treated for releasing at one surface so as to have a thickness
of 50 .mu.m after the solvent being removed by drying. As a release
sheet, a linear low-density polyethylene film (thickness: 110
.mu.m, surface tension: 32 mN/m) was applied onto the coated
surface, thereby a sheet to form a protective film for chips was
prepared.
[0179] The protective film forming layer of the sheet to form a
protective film for chips was applied on the ground surface of the
wafer using the dicing tape mounter, and a laminate thus formed was
fixed by a ring frame (FIG. 6-A).
[0180] The protective film forming layer was half cured by
ultraviolet ray irradiation dosed from the sheet side using the
ultraviolet ray irradiation apparatus A(not shown in the
figure).
[0181] The wafer, together with the protective film, was diced into
chips (10 mm.times.10 mm) using the dicing apparatus to obtain
objective chips having a protective film forming layer (FIGS. 6-B
and 6-C).
[0182] The respective chips were heated at 160.degree. C. for 1
hour suing the forced convection constant temperature oven (FIG.
6-G) to cure the protective film forming layer, thereby objective
chips having a protective film were obtained.
Example 5
[0183] The composition for the protective film forming layer 2 was
coated on the release-treated surface of a
polyethyleneterephthalate film (Lintec Co., Ltd. SP-PET3801) having
been treated for releasing at one surface so as to have a thickness
of 30 .mu.m after the solvent being removed by drying. As a release
sheet, a linear low-density polyethylene film (thickness: 110
.mu.m, surface tension: 32 mN/m) was applied onto the coated
surface, thereby a sheet to form a protective film for chips was
prepared.
[0184] The polyethyleneterephthalate film was detached from the
sheet to form a protective film for chips. The protective film
forming layer was applied on the ground surface of the wafer in the
same manner as in Example 1, and the peripheral edge of the sheet
was removed along the wafer shape (FIG. 2-A).
[0185] The protective film forming layer was half cured by
ultraviolet ray irradiation dosed from the sheet side using the
ultraviolet ray irradiation apparatus to eliminate its tackiness
(not shown in the figure).
[0186] After the release sheet was detached using the sheet
detaching apparatus (FIG. 2-B), the protective film forming layer
was completely cured by heating at 160.degree. C. for 1 hour using
the forced convection constant temperature oven (FIG. 2-C) to
prepare a wafer having a protective film.
[0187] The wafer, together with the protective film, was diced into
chips (10 mm.times.10 m in the same manner as in Example 1 to
obtain objective chips having a protective film (FIGS. 2-D and
2-E).
* * * * *